DoH endpoint ignores 'disallowed_clients' resulting in 'POST /dns-query: dns server is not running'

### Issue Details

* **Version of AdGuard Home server:**
* v0.104.3
* **How did you install AdGuard Home:**
* Docker
* **How did you setup DNS configuration:**
* System
* **Operating system and version:**
* Ubuntu 20.04

### Expected Behavior
The DNS over HTTPS (DoH) endpoint '/dns-query' should ignore any queries sent by a client on the disallowed client list.

### Actual Behavior
Clients on the disallowed client list are still able to send requests to the DoH endpoint '/dns-query', resulting in "POST /dns-query: dns server is not running" with high CPU load.